In a conventional solar heat collecting apparatus for absorbing solar heat energy, as shown in FIG. 1, a heat collecting tube 2 the inside of which is formed as a passage for a heating medium, is disposed in an outer tube 1 of transparent glass, and the spaces between the heat collecting tube 2 and the end open portions of the outer tube 1 are hermetically closed by glass end plates 3, each to which a metallic support tube 3' is disposed, and a glass exhaust tubulure 4 provided at the circumferential surface of the outer tube 1 is exhausted and calcined so as to be sealingly closed.
In such an arrangement to provide the relatively long glass outer tube 1 with the glass exhaust tubulure 4 requires troublesome work, and the exhaust tubulure 4 is susceptible to breakage because this tubulure 4 projects from the circumferential surface of the outer tube 1.
In addition to high manufacturing cost, thus manufactured solar heat collecting apparatus with the heat collecting tube 2 and the end plates 3 mounted requires very careful handling in transportation and installation, thus resulting in high handling cost.
It is an object of the present invention to provide a solar heat collecting apparatus in which an exhaust tubulure is provided at one of metallic end plates hermetically closing the end open portions of an outer tube of tranparent glass, thus reducing manufacturing cost.
It is another object of the present invention to provide a solar heat collecting apparatus which is easily handled.
It is a further object of the present invention to provide a more reliable and longer lifetime solar heat collecting apparatus in which provision is made for preventing damages to the exhaust tubulure and for strengthening the exhaust portion.
It is still another object of the present invention to provide a solar heat collecting apparatus in which various members may be hermetically sealed easily.